So I've been riding for three weeks now

[the chi]

Tached is dead on. Become confident and solid in basic riding skills and reactions before risking someone else's life (IMO). Personally, I dont ever carry 2 up, I dont care if I take myself out, but I wont be responsible for someone else.

To answer your wrist question, whenever you find yourself putting pressure on your wrists, consciously tighen your abs and use your back muscles to take all pressure off your wrists. Your hands should lightly rest on the grips. Its all a matter of practice. The more you remind yourself to take the weight off the wrists, the faster you'll be doing it without even thinking about it.